There is furtive behaviour going on in the front garden. A passer by stops and comments on the task I’m undertaking which is raking the leaves from the lawn and sweeping them up from the path. There are lots of them. This is a tree-lined street with a huge Lime tree in front of the house. She looks at me sorrowfully and says “it never ends” to which I nod, smile and reply “yes, but I don’t mind, I’m making leaf mould”.
This is one of the great joys of November, it’s late autumn and it brings one of the greatest harvest opportunities – free compost. I want to gather as many leaves as possible over this pleasant weekend. I’ve made leaf mould a couple of times and I know how extraordinary it is, my supply from two years ago is running short, so I’m committing to start the process again this year.
Leaf mould turns my hardened, sticky Gloucestershire clay soil into something much more manageable ready for the bulbs and dahlias that I so treasure in this part of the garden. It works wonders for my clay soil but it is also a fabulous conditioner for all types of soil, on thinner soils it helps to bind it together and gives it more body.
Making leaf mould is easy as long as you remember that the leaves need both air and moisture to rot down. The ideal way is to gather the leaves in a wire cage (chicken wire is good for creating one) and pack them in tightly as a lot of leaves are needed to make a decent amount. If you don’t have a wire cage or you’re tight on space, then you can pile the leaves into a bin bag and tie the top and move it somewhere more convenient. As long as you punch holes around the bag to allow for air and remember to water the leaves so that they remain damp this is as good a method as any and it’s how I’ve been making my leaf mould.
The alchemy of leaf mould is different to standard garden compost. Unlike ordinary composting the decomposition is based primarily by fungi rather than bacteria. The plus side to this process is that it makes it simple to make. Gather the leaves and the worms and weather will do the rest. There is no need for creating the heat that is needed for compost so there’s no requirement to turn it or move it from bin to bin.
The process is slower that ordinary composting and it will takes around 2 years for your leaves to become crumbly brown goodness. Leaf mould is quite nutrient poor so adding it to the soil will give better texture but won’t add potentially unwanted fertility. Being quite low in nutrients and with an open texture also makes it the perfect seed sowing compost. Though I’ve had to give it another year of rotting down to get leaf mould de-composed enough to be suitable for seeds (I then sieve the compost to get a lovely fine texture).
One of the key things that impacts on the length of time the composting process takes is the leaf type. In general the thicker the leaves the longer the process will take. I use a variety of leaves blown into and from the trees around the garden. The lime tree, acer, oak and apple tree leaves I’m happy to tie together in one bag as they will rot down pretty much at an even rate. If I’m harvesting thicker leaves like sweet chestnut trees then I’ll wait for a dry day and run the lawn-mower over them first to break them down a bit before gathering them together for the composting process. Evergreen leaves take a really long time, so if you want to make use of them run a mower over them to break them up and then they are best added to the main compost pile . Pine needles also take a really long time to breakdown but composted pine needles are fabulous for acid loving plants like the rhododendrons and pots of blueberries.
So, as I heap the third bin bag full into a corner of the garden, I know I can forget about them for a while and look forward to delicious sweet compost.